It is known in the prior art to prepare hydrophobic modified crystalline olefin polymers having good receptivity for dispersed dyes. Various processes for preparing such hydrophobic fibers from crystalline olefin polymers modified with unsaturated acids have been disclosed.
By "modified polymers" is meant such polymers which contain free functional groups grafted along the polymer chain and which impart particular chemical and chemical-physical characteristics to the olefin polymer.
Process for preparing the hydrophobic fibers is described e.g., in a recent patent application in the name of the Applicants. Said process consists in grafting carboxylic groups on crystalline olefin polymers by subjecting the polymer to a preliminary treatment with an organic peroxide and then reacting with an unsaturated carboxylic acid in the presence of an organic peroxide having different reactivity than that used in the preliminary treatment.
Such fibers, when subjected to the test of the measure of immersion time, which consists of introducing 1 g of fibers into a liter of distilled water at 25.degree. C. do not exhibit any hydrophilic characteristics even after long immersion times up to one hour.